Puget Sound must not be complacent in the face of the earthquake threat

Puget Sound's infrastructure, both buildings and social systems, should help it fare well in the face of the earthquake risk it faces in the next decades. But these guest columnists, board members of the Cascadia Region Earthquake Workgroup, urge the region not to be complacent.

The Cascadia Region Earthquake Workgroup and Pacific Northwest Seismic Network will host a public discussion of the impacts and responses to the Haitian and Chilean earthquakes and the lessons for the Pacific Northwest from 4 to 6 p.m., March 23, at the University of Washington, Johnson Hall, Room 102.

DO we have the same earthquake risks as Haiti? As Chile?

One just has to look at our majestic surroundings to realize that we also are being shaped by a comparable richness of tectonic processes. Like Haiti, many shallow faults similarly located close to our own urban centers are capable of producing powerful earthquakes. These include the Seattle, Tacoma, South Whidbey Island fault systems and others.

And, like Chile, off our coast there is the possibility of a huge megathrust earthquake on the Cascadia subduction zone — the interface between the Juan de Fuca and North American plates, which extends from Cape Mendocino in Northern California to the northern tip of Vancouver Island.

The risk earthquakes pose depends not only on natural events, but also on the vulnerability of our environment and how we prepare and respond. For reasons we are all too aware of now, Haiti's built and social structures demonstrably lacked the resilience needed to survive the shaking, despite the fact the earthquake risk was documented and the vulnerability of many of the country's systems understood.

On the other hand, Chile has a long history of living with, preparing for and responding to earthquakes. This is evident in the fact that although the Chilean earthquake released about 500 times the energy of Haiti's, their buildings have fared much better — a remarkable testimony to the efficacy of adhering to building codes designed to keep structures standing after a strong earthquake.

In the Northwest, we should take comfort in knowing we have taken actions to reduce our own vulnerability. Most buildings are built to modern codes that have proven to result in safer structures. We have redundant systems and our preparations for other disasters will help us recover from earthquakes.

However, critical aspects of our transportation infrastructure, including the Highway 520 floating bridge and the Alaskan Way Viaduct and sea wall, are vulnerable to earthquake shaking. Other critical lifelines such as ports and pipelines are also vulnerable and their failures would hinder relief and recovery efforts, potentially with a long-term economic impact. Understanding these risks is important, and mitigating them represents a clear path toward improving our resiliency.

We cannot be complacent. We have a threat and a real risk. Collectively, all the faults in the region give us a 7 percent chance of a experiencing a Haiti-style earthquake in a 50-year time window and the chance of a Chile-like earthquake along our subduction zone is slightly greater — very hefty likelihoods in most of our lifetimes.

While we have fared well in the moderate and large deep earthquakes that have occurred in the last 70 years, the largest ones (in 1949, 1965, and 2001) were different from the earthquakes that struck Haiti and Chile and that we can expect in Puget Sound. The significantly greater depths of these past events put extra distance between the earthquake and us, allowing destructive energy to dissipate before reaching the surface where we live.

Residents of Puget Sound also have not experienced the repeated shaking from aftershock activity that accompanies shallow and megathrust earthquakes. As in Haiti and Chile, we will have to respond and recover over months and years while our structures and psyches continue to be shaken.

Although exacerbated in Haiti by its island geography and less-resilient infrastructure, both countries experienced failures of their communications systems and consequent information vacuums and chaos immediately following and, in spots, for days after the earthquakes. We can expect the same in the Pacific Northwest, although the recovery time frame may be shorter.

Geophysicist R. Bilham writes, "In recent earthquakes, buildings have acted as weapons of mass destruction." Perhaps the clearest lesson of the Haitian and Chilean earthquakes is that we must support the adoption and enforcement of building codes, the funding that strengthens our infrastructure, and programs that help prepare our communities.

For more information we encourage you to visit www.crew.org. We encourage you to download the new Cascadia Region Earthquake Workgroup (CREW) Shallow Earthquake and the Cascadia Subduction Zone scenario pamphlets and begin implementing the state of Washington Emergency Management 12-step preparedness process accessible from the CREW "Home Owners" Web-site link. We all have a role in preparing our community for a natural disaster.

Andre LeDuc is executive director of the Oregon Partnership for Disaster Resilience at the University of Oregon. John Schelling is earthquake program manager for Washington State Emergency Management. Cale Ash is a project engineer at Degenkolb Engineers. Le Duc is president is of the Cascadia Region Earthquake Workgroup; the others are board members.